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Cellular energy allocation (CEA) test was performed in order to investigate the effects and costs of bare carbon nanotubes (CNTs) and CNTs in combination with titanium dioxide nanoparticles (CNTs/TiO₂-NPs) on Glyphodes pyloalis Walker after 24, 48 and 72 hours of exposure to 100, 200, 300, 400 and 500 ppm of the treatments. Results showed the negative correlation between total lipid amounts and concentrations of treatments (i.e. CNTs and CNTs/TiO₂-NPs) as well as exposure time. Contrary to CNTs treatments, carbohydrate contents were affected by both of CNTs/TiO₂-NPs concentration and time of exposure. Results showed that the effect of bare CNTs in the enhancement of glycogen content appeared significantly faster than that of CNTs/TiO₂-NPs. Increasing time of exposure to all concentrations of CNTs, except for 100 ppm, prevented enhancement of protein content. The effect of bare CNTs on the reduction of protein contents was faster and greater than that of CNTs/TiO₂-NPs. The results indicated that G. pyloalis cannot regulate internal CNTs and CNTs/TiO₂-NPs concentrations efficiently without considerable impact on the energy reserves (Ea). The comparison of energy consumed (Ec) in treated larvae showed that CNTs/TiO₂-NPs reflected the higher energy demand of the stress response than CNTs. Generally, CEA was significantly decreased as the concentration of CNTs treatments increased. More reduction in CEA amount of all treatments by CNTs/TiO₂-NPs than that of the control is also probably considered as a cost to deal with detoxification when the concentration increased and at all the tested time points. Therefore, CEA test might be considered as an early biochemical biomarker for assessing immediate response of organisms after acute exposure to stressors and thus could be applied to risk assessment of nanomaterials.

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Organophosphates (OPs), one of the most important pesticide groups, are used worldwide to control pests. Acetylcholinesterase (EC 1.14.18.1) (AChE), an enzyme from insects’ nervous systems, is the leading target site of this group of pesticides, such as Acephate. Inhibition of enzyme activity through Acephate-derived compounds can control both resistant and non-resistant pests to OPs. In this research, the toxicity of these compounds was assayed regarding the control of Xanthogaleruca luteola (Muller). Results of the in vivo screening test revealed that two derived compounds of phosphorhydrazides (PHA) (i.e., NH₂-C(O) NH-NH P(O)(OC₆H₅) and OC₄H₃-C(O)NH-NHP(S)(OCH₃)₂) showed the most significant insecticidal potential. AChE was purified and isolated from the third instar larvae of elm leaf beetle, X. luteola, using affinity chromatography. IC₅₀ values, inhibition mechanisms, and inhibitory constant (Ki) of NH₂-C(O) NH-NH P(O)(OC₆H₅) and OC₄H₃-C(O)NH-NHP(S)(OCH₃)₂ as inhibitors were calculated for the purified AChE. These compounds inhibited acetylcholinesterase (AChE) and general esterases of third instar larvae of elm leaf beetle. These compounds, by mix inhibition mechanism, inhibited AChE enzyme, and K_i obtained was 1.16 and 0.88 µM^-1 min^-1 for NH2-C(O) NH-NH P(O)(OC6H5) and OC4H3-C(O)NH-NHP(S)(OCH3)2, respectively. QSAR study based on multiple linear regressions (MLR) and principal component analysis (PCA) showed that the non-descriptor net charge of the nitrogen atom influenced by the polarization of N-H group had the most significant effect on the insecticidal potential. Therefore, designing new compounds that control the N-H polarization of the nitrogen atom could be an excellent option to study insecticidal properties of Acephate-derived compounds.
 

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The cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae), is an important pest of canola that can considerably limit crop production through direct or indirect damage. In this study, the effects of Azadirachtin, Tondexir, Palizin, and Thiamethoxam, common insecticides used in managing the cabbage aphid, were investigated on the population growth parameters of this pest. Based on the results, the LC₅₀ values for Thiamethoxam, Palizin, Azadirachtin, and Tondexir were 0.19, 0.63, 1.00, and 3.82 g/L, respectively. Moreover, LC₃₀ concentrations of Thiamethoxam, Palizin, Azadirachtin, and Tondexir were 0.11, 0.10, 0.41, and 1.68 g/L, respectively, applied in the sublethal studies. The cabbage aphids reared on the plants treated with these insecticides had lower longevity, fecundity, and reproductive period than the control treatment. The intrinsic rate of increase (r_m), finite rate of increase (λ), net reproductive rate (R₀), and generation time (T) were lower on Thiamethoxam treatment. Tondexir and Palizin treatments had lower values than Azadirachtin. However, there was no significant difference between the Tondexir and Palizin treatments. The population treated by Azadirachtin had the highest values of growth parameters. According to the results and available information in the context of risk assessment of the studied insecticides, this research recommends the application of Thiamethoxam in the integrated pest management of cabbage aphid.

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 The toxicity of chlorpyrifos to three Iranian populations of two-spotted spider mite, collected from Isfahan (ISR), Yazd (Yz) and Guilan (GUS2) Provinces were surveyed using the residual contact vial bioassay. The bioassay results showed that resistance ratios of ISR and Yz populations were 176.90 and 9.78 fold compared to the GUS2 population, respectively. Determination of esterase and glutathione-S-transferase activity and their kinetic parameters showed that ISR population had the highest specific activity and specificity constant among the studied populations. Besides, the content of mixed function oxidases in ISR population was the highest. However, synergistic effects of Piperonyl Butoxide, Diethyl Maleate and Triphenyl Phosphate showed that metabolic enzymes did not play an important role in resistance to chlorpyrifos in ISR and Yz populations and enhanced activity of esterase, glutathione-S-transferase and content of mixed function oxidases in these populations were probably due to resistance to some other acaricides. To determine the role of acetylcholinesterase insensitivity in resistance mechanisms, kinetic parameters and inhibitory effect of chlorpyrifos-oxon on this enzyme were investigated. The K_m value of acetylcholinesterase was determined as 0.036, 0.04, and 0.050 mM using acetylthiocholine iodide for GUS2, Yz, and ISR populations, respectively. In addition, the insensitivity ratios of chlorpyrifos-oxon on acetylcholinesterase activity were estimated at 23.30 and 2.96 for ISR and Yz populations, respectively. These results confirmed amino acid substitutions in active site of this enzyme and also indicated that resistant population possed qualitatively altered AChE.

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Application of chemical pesticides has increased significantly worldwide and has raised serious concerns about environmental pollutions. One of the encouraging trends to minimize pesticide risk is production of resistant plants containing toxic proteins against insect pests. Considering the importance of purification and characterization of digestive enzymes in the production of resistant plants, in this study an α-glucosidase from the Naranga aenescens Moore's midgut was purified by ammonium sulfate precipitation, ion exchange chromatography on DEAE-sepharose, and concentrating through ultrafiltration. The apparent molecular mass of the enzyme was 48 kDa determined by SDS-PAGE. The optimum pH and temperature of the enzyme were 6.0 and 45°C, respectively. The irreversible thermoinactivation of the enzyme showed that it was highly stable at 35ºC but moderately stable at 40 and 45ºC. Zn²⁺, Hg²⁺, Co²⁺ at 10 and 20 mM, and Ba⁺²only in 20 mM strongly inhibited the α-glucosidase activity. Ba²⁺ and Ca²⁺ only at 10 mM, EDTA and Hg₂²⁺ only at 20 mM and Mg²⁺ at 10 and 20 mM significantly increased the enzyme activity. The K_m and K_cat values for the α-glucosidase were 0.54 mM and 3.62 min^-1, respectively, when p-Nitrophenyl-α-D-glucopyranoside (pNαG) was used as a substrate.